Theoretical, structural, and spectroscopic studies of a series of Ni II(TRISOXH 3)X 2 complexes

Abstract

A series of nickel tris(oxime)amine complexes, including Ni(TRISOXH 3)Br 2 ( 2), [Ni(TRISOXH 3)(MeOH)I]I ( 3), and [Ni(TRISOXH 3)(H 2O) 2]F 2 · 2H 2O ( 4), was studied using modern density functional theory in combination with experimental methods (X-ray crystallography, Raman, and infrared spectroscopy). The series was compared to Ni(TRISOXH 3)Cl 2 ( 1), for which a detailed evaluation of theoretical models has been previously reported [R.M. Jones, M.J. Baldwin, J. Phys. Chem. 108 (2004) 3537]. The application of the theoretical model and the influence of changing the secondary ligands on nickel–TRISOXH 3 interactions are evaluated. The crystal structures of 2, 3, and 4 show similar coordination geometries with some noted differences attributed to the different ligands. Unrestricted optimized geometry and frequency calculations were performed with the hybrid density functional B3LYP and split basis sets. Optimized geometries show small average absolute deviations for intraligand (0.016 Å) and metal–ligand bonds (0.042 Å) when compared to experimental crystal structures. The most intense vibrational modes of 2, 3, and 4 were assigned with the aid of a modified wavenumber linear scaling procedure, which resulted in 2- to 3-fold improvement in the agreement between experimental and theoretical wavenumbers. Derived linear scale functions for 1 can be successfully applied to theoretical frequencies of 2 and 3, but yield minimal improvement in the agreement between experimental and theoretical frequencies when applied to the frequencies of 4. Natural charge and unpaired spin distribution are evaluated for comparison of electronic influences of the varied ligands on metal–oxime interactions.